東京 Crystal 勉強会 #1 in 五反田

1. router-simple.cr
id:karupanerura

2. about me
• @karupanerura (Twitter/Github/etc..)
• Perl/Swift/C/Java/etc..
• Crystal/Ruby beginner
• Lead Engineer of Mobile Factory, Inc.
• Talk on YAPC::Asia/YAPC::EU 2015

3. router-simple?

4. URI(Path) Router

5. Example:
require "router-simple"
dispatcher = Router::Simple::Dispatcher(Hash(Symbol, String)).new()
dispatcher.add("/", {
:controller => "Root",
:action => "index",
})
dispatcher.add("/users/:user_id", {
:controller => "Users",
:action => "fetch_by_id",
})
dispatcher.match("/") {|result|
p result.route.meta[:controller] # => "Root"
}
is_match = dispatcher.match("/users/1") {|result|
p result.route.meta[:controller] # => "Users"
p result.match["user_id"] # => "1"
}
p is_match # => true (it means that is matches the route!)

6. Repository:
https://github.com/karupanerura/router-simple.cr

7. My favourite points

8. My favorite points
• Ruby like syntax
• Type safety + Optional type restrictions
• Nil safety (#.not_nil!)
• Generics
• Using PCRE

9. Ruby like syntax
• module/class/require
• Dependency on Projectfile
• &block + yield
• *args
• etc..

10. Optional type restrictions
def foo() : String # = String
return "Foo"
end
# or
def foo() # = String
return "Foo"
end

11. Nil safety
def foo() : String? # = String|Nil
return "Foo" # or nil
end
foo = foo()
if foo != nil then
foo.not_nil! # = String
end
# foo.length => compile error!!

12. Nil safety
• implementation is very simple!
• https://github.com/manastech/crystal/
blob/master/src/object.cr#L149
• https://github.com/manastech/crystal/
blob/master/src/nil.cr#L117

13. Generics
• Optional typing + generics = great!
• MyClass(T) and use it.
• POINT: Type specialization is supported
• POINT: Type restriction is optional.

14. Using PCRE
• Perl5 hacker loves PCRE :)
• Perl extended regexp is available

15. How to create
library on Crystal?

16. $ crystal lib create Foo::Bar

17. OK. Let’s write it!

18. Thank you for listening!